import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner num = new Scanner(System.in);
        int r1 = num.nextInt();
        int r2 = num.nextInt();
        double R = 1.0/((1.0/r1)+(1.0/r2));
        System.out.println(R);
    }
}
